The present invention generally relates to an apparatus for moistening the flap of an envelope in a high speed mail processing machine, and more particularly to heating the liquid used for moistening envelope flaps in such a machine.
In mail processing machines, moistening devices are used to wet the flap of an envelope in preparation for sealing the envelope. Conventionally, flap wetting is accomplished by feeding the envelopes flaps past a moisture applicator such as a brush, a wick, or other moist surface, allowing the moist surface to come into contact with the glue on the envelope flap. The moisture causes the glue to soften and to become sticky. The moistened envelopes flaps are closed and the glue is pressed between the flap and the body of the envelope to form a seal. The envelope is then either ejected into a stacker, or passed on to another part of the mail processing machine for further processing.
Current mail processing machines are often required to process up to 18,000 pieces of mail an hour, and envelopes travel at speeds as high as 100 inches per second as they are being processed. As a result, the steps of moistening and sealing the envelope flaps must occur very quickly. In such a high speed environment, conventional moistening and sealing devices can result in a poor seal because the glue has inadequate time to absorb enough moisture before the flap is closed. In high speed systems, moisture may not have time to penetrate and fully moisten glue to allow an effective seal. If the envelope flap is closed before the glue is adequately softened, the flap may partially or fully open during further high speed processing, and possibly jam the machine.
Also, with envelope flaps moving by the moistening applicators so quickly, there is less time for water to flow from the applicator to the envelope flap. Thus it is desirable to facilitate the flow of water out of the applicator to ensure that adequate moisture is applied to the glue on the envelope flaps.
The present invention provides an envelope moistening and sealing system in which the liquid used to moisten the glue on the envelope flaps is heated. The heated liquid softens the glue more quickly, providing an improved seal for an envelope in a high speed mail processing machine. In the preferred embodiment, the heating element can be molded directly into the walls of the reservoir tank.
The reservoir is also adapted to control the liquid level by feeding liquid in through an inlet, and draining liquid out via an outlet drain located at the desired liquid level. The flow of liquid from the inlet to the drain serves to refresh the liquid in the reservoir and to slow the accumulation of biological material in the reservoir. The reservoir is also equipped with a splash receptacle around the perimeter of the reservoir to retain liquid that might splash out of the main reservoir volume when the machine is moved or bumped.
The heating element of the system can also be adapted for use as a low liquid sensor by monitoring the rate at which the heating element heats. If there is little or no liquid in the system, the heating element overheats or heats more quickly and a low liquid alarm is activated.